<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
        .box{
            width:800px;
            background: red url() 0 0 no-repeat;
            margin: 0 auto;
        }
        .box:after{
            content: "";
            clear: both;
            display: block;
        }
        /*.box:before{
            content: "bbb";
        }*/
        .box1{
            width:800px;
            height: 120px;
            background: yellow url() 0 0 no-repeat;
            margin: 0 auto;
        }
        .left{
            float: left;
            width:40%;
            height: 50px;
            background: blue url() 0 0 no-repeat;
        }
        .right{
            float: left;
            width:60%;
            height: 50px;
            background: green url() 0 0 no-repeat;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="left"></div>
        <div class="right"></div>
    </div>
    <div class="box1">
    </div>
</body>
</html>